Anyone have the comp lim of the nrgkits era , and can tell the story about it .On the all web , i only found 1 video . They said in manual that it keep the broadcast modulation to 100 in FM 100 mean 75khz . is that correct and true ? as it only act as AGC and some release or attack by jumper set .i found a pcb board unmounted , and it is selled also , and of course i could not bue it , but love to listen to it is story .

the one I had sounded very good, the leds would blink on and off, were quite good before sound solution st tool came along. It would make everything sound more bright though it was live from what I remember, I suppose not everyone would be of fan that suppose they just want the volume going up and down with the material, only experience is using it in mono, I suspect for stereo you'd want something of that nature.

The NRG limiter was based on an old design that Stephen had developed from examining commercial broadcast limiters. The sidechain was converted from an old transistor-based circuiit, and the use of the quad op-amp packages made construction easier. The use of the BLR-series 15kHz low-pass filter eliminated the need for high accuracy components that would be needed if op-amp filters were used, and also simplified the circuit requirements a lot.

The LED indicator to show the degree of limiting was too imprecise to be much use, but it looked good to the unintiated! Stephen did try a split-band version of the limiter, with two bands - bass <240Hz and everything else - and this sounded much "louder" on the air, because it could be pushed harder. Loud bass content didn't cause the rest of the audio to "dip", and with a bit of tweaking, it could sound really good.

The limiter did have other limitations too. There was a problem with it missing really sharp transients, and allowing them to sneak through, and there was no way to further speed up the "attack" without introducing lots of distortion. The ones that went for use on RSLs had a guard clipper on the output with a further 15 kHz lowpass filter block to get rid of any harmonics that the clipping action caused.

When Stephen died, I had been working on a "Pro IV" limiter, that was to use PWM for the attenuation, and this was to be provided on a board the same size as the Pro IV stereo coder, and installed as an "above" board, connected after the pre-emphasis stage. We also planned to offer a two-band version as well. I've got the documentation here somewhere....

Thank you . Really like that explanation in deep, but what about quiet piece of sound , or loud sound , does it maintain at a constant level , if it has been seen on a dev meter ?

We checked the design extensively on a good deviation meter! The circuit doesn't really compress - it does virtually nothing until you get to around 6dB below peak deviation - it's real LIMITER! If you want an AGC function to cater for a range of input levels, you'd have to use a futher piece of kit (I designed a slow-acting AGC for just this purpose, but we never released it).

Oh thanks again , everyday new information.
Can you post a picture of an assembled one .

I always thought they were more like a vu meter, suppose something like a vu meter could show a basic level, used to have one in pcs 3w, it looked good, I do miss that to be honest. I always though the nrg limiter was used in rsl’s they were nearly always in mono, don’t know why stereo wouldn’t cost extra, they were just charged by the rf/time on air, suppose mono would make the signal sound clearer I guess. Just me though I guess stereo always sounds more professional, even if you have more noise on it, something mono sounds unlicensed, just my opinion, obviously mono has advantages less equipment for them to hire out I suppose, but if they've got an nrg limiter they could of got an nrg stereo encoder.

Transmitting in mono really doesn't change the equipment much - most studio equipment is in stereo so there's nothing to be saved in being in mono. Where it does make a difference is coverage.

Stereo requires at least a 6 dB stronger signal and more realistically 14 dB (figures taken from ITU-R Recommendation BS.412). Assuming a best case 6 dB difference, this means that a low power 25 W transmitter will provide the same 'quality' of reception for mono at twice the distance (e.g. 4 times the area) compared to 25W in stereo. Obviously terrain and obstructions play a role but you're going to get much more solid coverage in mono than stereo and when you're running low power this can make a big difference to the way that average listeners perceive reception. If the signal sounds 'hissy' then they will turn off. If you keep it in mono, many won't even notice the lack of spatial diversity but their hissy-fits are gone.

Also - it's no good transmitting the 19 kHz tone to 'light the stereo pilot light' but not transmitting in stereo. This is the worst by far as you'll get all the hiss but none of the counterbalancing stereo audio that can at least mask some of the sssssssssssssssss

The only saving grace is most car radios nowadays are pretty good at dropping back to mono automatically when the signal gets noisy

Wow . so why i always prefer trxing in mono over stereo , because of the low gain antenna GP and my 30w Pa .
Thanks guys .iI am planning to make my own 50-70W Pa wich use a mosfet that i found in a local market , seems to be original , but cost a bit more , it is an RD70, i am trying to find a layout for it .

radium98 wrote: ↑Wed Oct 08, 2025 6:46 am Wow . so why i always prefer trxing in mono over stereo , because of the low gain antenna GP and my 30w Pa .
Thanks guys .iI am planning to make my own 50-70W Pa wich use a mosfet that i found in a local market , seems to be original , but cost a bit more , it is an RD70, i am trying to find a layout for it .

Is it a RD70HUF2 or RF70HVF1 or RD70HHF1? Seems to be few variaitons on the RD70.

RD70HUF2 Datasheet : https://www.mitsubishielectric.com/semi ... 70huf2.pdf

RD70HVF1 Datasheet :
https://www.alldatasheet.com/datasheet- ... 0HVF1.html

RD Datasheet List :
https://www.alldatasheet.com/view.jsp?Searchword=RD70

My first RD70HVF1 amplifier ran at around 85 Watts out on a car battery supply (13.8V) when driven with 3.8 Watts from an NRG Pro III board. It needed a huge heatsink (blowers were not an option), but it worked really well down at 87.5 to 88.5 MHz. Even before the output LPF, the second was -50dBc, and fitting a trap and LPF cleaned it up nicely so that nothing was seen on the SA except the carrier. The rig was housed in a plastic milk crate, and was used at a couple of European festivals in the early years of this century. After its first use, it gained a stereo coder, a stereo limiter and a couple of MP3 players, so it became a useful standalone battery-powered radio station!

radium98 wrote: ↑Tue Oct 07, 2025 6:54 am Oh thanks again , everyday new information.
Can you post a picture of an assembled one .

built a year ago

few more pics